Remember if a user declines to provide a server with a client certificate

net/base/ssl_client_auth_cache.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/base/ssl_client_auth_cache.h"
 
+#include "base/logging.h"
+#include "net/base/x509_certificate.h"
+
 namespace net {
 
 SSLClientAuthCache::SSLClientAuthCache() {}
 
 SSLClientAuthCache::~SSLClientAuthCache() {}
 
-X509Certificate* SSLClientAuthCache::Lookup(const std::string& server) {
+bool SSLClientAuthCache::Lookup(const std::string& server,
+                                X509Certificate** certificate) {
+  DCHECK(certificate);
+  *certificate = NULL;
+
   AuthCacheMap::iterator iter = cache_.find(server);
-  return (iter == cache_.end()) ? NULL : iter->second;
+  if (iter == cache_.end())
+    return false;
+
+  *certificate = iter->second;
+  return true;
 }
 
 void SSLClientAuthCache::Add(const std::string& server,
                              X509Certificate* value) {
   cache_[server] = value;
 
   // TODO(wtc): enforce a maximum number of entries.
 }
 
 void SSLClientAuthCache::Remove(const std::string& server) {
   cache_.erase(server);
 }
 
 }  // namespace net